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Experimental Design in fMRI A voxel in tissue that responds to the task shows signal change that matches the timecourse of the stimulus ActiveRestActiveRest 60 sec Signal

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Structural and Functional Imaging The colour in an fMRI image indicates how well the signal at each voxel matches the pattern of active and rest blocks.

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Structural and Functional Imaging The coregistered functional image has a mask so that all voxels that dont match the stimulus pattern in time are set to be transparent…thats why you see the anatomical image underneath

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PET: another way to measure blood Oxygenation Positron Emission Tomography (PET) Injects a radioisotope of oxygen PET scanner detects the concentration of this isotope as it decays

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Advantages of fMRI Advantages of MRI: 1.Most hospitals have MRI scanners that can be used for fMRI (PET is rare) 2.Better spatial resolution in fMRI than PET 3.Structural MRI is usually needed anyway 4.No radioactivity in MRI 5.Better temporal resolution in MRI

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Advantages of PET Advantages of PET: 1.Quiet 2.A number of different molecules can be labeled and imaged in the body

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Limitations of fMRI All techniques have constraints and limitations A good scientist is careful to interpret data within those constraints